Ornithological Monographs 13

EVOLUTIONARY
IN

TRENDS
THE

NEOTROPICAL

AND

OVENBIRDS

WOODHEWERS

BY

ALAN

ORNITHOLOGICAL

FEDUCCIA

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'
1973

NO.

UNION

13


EVOLUTIONARY
IN

TRENDS
THE

NEOTROPICAL
AND

OVENBIRDS

WOODHEWERS

BY

ALAN

ORNITHOLOGICAL

FEDUCCIA

MONOGRAPHS
PUBLISHED

THE

AMERICAN

BY

ORNITHOLOGISTS'

1973

NO.

UNION

13


ORNITHOLOGICAL

MONOGRAPHS

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Ornithological
Monographs,
No. 13, iv q- 69 pp.
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TABLE
INTRODUCTION

Woodhewer

Ovenbird

CONTENTS

.......................................................................................

COMPARATIVE ANATOMY

Anatomical

OF

material

OF THE SKULL .................................................
.......................................................................

9
11

skulls ...............................................................................

skulls

12

.....................................................................................

14

Philydorine skulls ...........................................................................

17

Skulls of the "intermediates" _.................................................................

22

Jaw muscles .........................................................................................

24

Functionalaspectsof the skulltypes................................................

25

STERNUM ...............................................................................................
EVOLUTION OF THE SCANSORIAL FOOT .................................................

Limb proportions........................................................................
Distal end of the tarsometatarsus .........................................................
Femur and tibiotarsus ....................................................................

34
36

ß..... 36
41
42

The digits .............................................................................................. 43
TAIL ............................................................................................................

45

SYRINGEAL ANATOMY ...............................................................................

45

ELECTROPHORESISOF HEMOGLOBIN .......................................................
Methods and materials .........................................................................
Results and discussion .....................................................................

48
48
49

CLUSTER ANALYSIS .................................................................................

51

A PHYLOGENY ......................................................................................

59

A BEHAVXORIAL MODEL .......................................................................

61

CLASSIFICATION .................................................................................

64

SUMMARY

65

LITERATURE

..........................................................................................
CITED

.............................................................................

68


INTRODUCTION

The Neotropical ovenbirds (Furnariidae) and woodhewers (Dendrocolaptidae)have long been consideredto be closelyrelated on the basisof
derivedcharacters
whichare sharedby the two groupsbut not foundin other

suboscine
birds. Generalplumagepatternsin the two groupsare amongthe

significantly
strikingsimilarities,as almostall species
havelight brownto reddish-brownbodyplumagewith variousdegreesof spottingon the breastand
back,oftenwithlightthroatpatches.A spinytail,usuallyof chestnut
or ferruginouscolor,whichis usedin the woodhewersas a bracein climbing,is found in
variousdegreesof development
in many membersof the Furnariidaeand is
well developedin certainovenbirdswhich foragelike the woodhewers,by

climbingup tree trunks. These scansoffalfurnariids,includingPseudocolaptes,Xenops,Pygarrhichas,
the Margarorniscomplex,and somespecies
of Cranioleuca,
are of interestin that, althoughthey are behaviorallysimilar
to the woodhewers,
beingtree-trunkforagersand possessing
stiff, spinytails,
they are clearlymembersof the Furnariidaeon the basisof suchcharacters
asthe syrinx,cranialmorphology,
andfeet. Commonwingpatternsare found
in the Furnariidaeand Dendrocolaptidae.
In addition,syringealand osteologicalcharacters
ally thetwo groups.It is onlywithinthe Dendrocolaptidae
and Furnariidaethat two pairs of intrinsicsyringeal(tracheo-bronchial)
musclesare found (Ames, 1971).

This sharingof characters
hasled manyornithologists
to question
the distinctness of the two families. Thus the familial classification of the furnariids

and dendrocolaptids
haslong beenin a stateof uncertainty,and at present

thereis little agreement
amongornithologists
concerning
the recognition
of
familiesin the group. Recentclassifiers
havegenerallyfollowedeithervon
Ihering(1915), who presented
evidencewhichhe considered
favoredmergingthetwofamilies,or Ridgway(1911), whorecognized
twofamilies.Stresemann (1934) unitedthe ovenbirdsandwoodhewers
into onefamily. In 1951
threeclassifications
wereproposed.Wetmore(1951) retainedtwo families
becausehe consideredvon Ihering'sevidenceinconclusive;
Peters (1951)
alsorecognizedtwo families. However,Mayr and Amadon (1951) treated
the entiregroupas a singlefamily, as did Storer (1960).
Early classifiers(see Garrod, 1873; and Beddard, 1898) placedconsiderable importanceon the conditionof the nasal bones in the classificationof
the higher categoriesof birds. Two basic arrangementsof the nasal openingswere distinguished,
schizorhinaland holorhinal. In the former, the nasal
openingextendsposteriorto the nasal-frontalhinge; in the latter, the posterior extentof the openingis anteriorto the hinge. The conditionin Furnarius and other ovenbirds,which was originallytermed schizorhinal(see Garrod, 1877), was later recognizedas not homologousto the conditionin other
1


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schizorhinalbirds (charadriiform birds, etc.), and F'tirbringer(1888) proposedthat the term pseudo-schizorhinal
be appliedto the conditionin those
ovenbirdsin which the posteriorextent of the nasalopeningis rounded,insteadof endingin a slit asin "true"schizorhiny.
Garrod (1877) emphasizedthat the conditionof schizorhiny(= pseudoschizorhiny)in the ovenbirdswasof sufficienttaxonomicimportanceto separatethe groupfrom the holorhinalwoodhewers.However,Garrod had examinedonly a small numberof species.Von Ihering (1.915) examineda
muchlargerseriesof speciesand concludedthat therewas actuallyno clearcut divisionbetweenthe pseudo-schizorhinal
ovenbirdsand the woodhewers,
and that the differencesbetweenpseudo-schizorhiny
and holorhiny representedslightmodifications
from a basicpatternand were thereforeof little
taxonomicimportance,exceptperhapsin characterizinggenera. Ridgway
(1911), however,had maintainedthat the differencein the arrangementof
the nasal openingplus the differencesin the feet were of sufficientimportanceto separatethe Dendrocolaptidae
from the Furnariidae. In the Furnariidae(sensuRidgway)the outertoe is shorterthan the middletoe and the
hallux without the claw is not shorterthan the inner toe (no. II) without the

claw. The middletoe is unitedto the outertoe by lessthanthe wholeof the
secondphalanx. In the Dendrocolaptidae
(sensuRidgway) the outer toe is
aboutas long as the middletoe and muchlongerthan the inner toe, and the
hallux without the claw is shorter than the inner toe. The three anterior

toesareunitedfor the entirelengthof the basalphalanx,andthe middletoe

is fusedto the outerby almostthe full extentof the secondphalanx.
Ames(1971) in hissystematic
conclusions
of the Furnariiemphasized
that
the syringealmusculatureof the ovenbirdsand woodhewers
was an indication
of closeaffinityof the two groups.Bothgroupspossess
two pairsof intrinsic
syringealmuscles,a characterwhich separatesthe two families from the
antbirds (Formicariidae) and tapaculos(Rhinocryptidae). However, the
ovenbirds
are apparently
separable
from thewoodhewers
on the basisof the
absencein the ovenbirdsof horns on the Processivocales (except in the

genusGeositta). It is alsoof interestto note that thereis far more syringeal
variation

within the Formicariidae

than within the woodhewer-ovenbird

as-

semblage.
Attemptsby many classifiers
to place animalsinto distinguishable

groups
without examiningin detail the charactersinvolvedhas led in many cases
to classifications
basedon the most adaptivefeaturesof the birds, namely
the bill and feet (the classicalexamplebeinghawks and owls which were at
one time classified
togetheron the basisof havingsimilarfeet and bills) with
little emphasison decipheringthe evolutionarypathwaysinvolved. The problem in the woodhewer-ovenbird
groupshas been the same as that for other


1973

EVOLUTION

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Figure 1. Two "strong-billed"
woodhewers,
an "intermediate,"
and two philydorine
furnariids.From top to bottom: Xiphorhynchu.•
lachrymos'us'
(actuallength,229 ram),

Xiphorhynchusguttatus',Dendrocinclaanabatina,Syndactylasubalaris,Automolus
ochrolaemus.


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groupsof passerine
birdswherethereis a largeamountof adaptiveradiation
for particularmodesof life.
The woodhewer-ovenbird
problemis of interestfor severalreasons.First,
the two groupsare very closelyallied,yet exhibitperhapsthe greatestadaptire radiationin any group of New World passefinebirds, with climbing

formsapparently
havingevolvedindependently
in manysituations.Second,
cranialmorphology
in the two groupsdiffers;therefore,the possibility
of
resolvingthe polarityof this evolutionexists. Most important,however,are
four genera,Dendrocincla,Sittasomus,
Deconychura,and Glyphorhynchus,

whichare normallyplacedin the Dendrocolaptidae
becausetheypossess
most
of the characters
of that family, but whichshowother characters
that ally
them with the Furnariidae. These forms, which I shall term the "intermediates,"form the startingpoint of this study (see Fig. 1).

Initially, my main interestwas in the evolutionof the differenttypesof
cranialmorphology
in the ovenbirdsand woodhewers.An examination
of
the skulls of woodhewersshowedthat most forms of the Dendrocolaptidae

conformed
to a basicpattern.Thesegenera,whichincludeall of the woodhewersexceptthe four intermediates,
are the formsthat I shall term the
"strong-billed"dendrocolaptids;
they appear to representa monophyletic
groupon the basisof the skull and other characters.The "intermediates,"
Dendrocincla,Sittasomus,Deconychura,and Glyphorhynchus,
are of particularinterest.Exceptfor Dendrocincla(whichforagesin a varietyof postures) the "intermediates"
are behaviorallylike the woodhewers
in that they
forageby hitchingup treetrunks.They alsopossess
the woodhewer
type of
syrinxand foot arrangement.However,they are clearlyintermediate
betweenthe holorhinaland pseudo-schizorhinal
types of nasal bone arrangements. Further, it was of interestto find that, of the four subfamiliesof the

Furnariidae(whichappearto be fairly well defined),the membersof the
subfamilyPhilydorinae,
the forest-dwelling
furnariids,are the formsthat possessan intermediate
arrangement
in the conditionof the nasalbones,and
some,suchas Hyloctistesand Automolus,are similar to the "intermediate"
woodhewersmentioned above. The other subfamiliesof the Furnariidae, the

Synallaxinae,
Furnariinae,and Sclerurinae,
are composed
almostentirelyof
memberswhichare pseudo-schizorhinal,
althoughin somespeciesthe nasal
foramen is somewhat shortened.

This interesting
situationled me to a literaturesurveyin whichI foundthe
oneimportantpaperon the relationships
of the woodhewers
and ovenbirds,
that of yon Ihering (1915). In it he discusses
the findingsof his investigations of the cranial morphologyof the two groupsand recordsmuch the
same observationsthat I have discussedabove. He stated (1915:

147) that,

"Pronounced
holorhinyis foundonly amongthe Dendrocolaptinae

of which,


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however,somegenera... Sittasomus,
Dendrocinclaand probablyothers...

are typically schizorhinal."At that time he had not examinedthe genera
Glyphorhynchus
andDeconychura.He furtherstatedthat, "The Philydorinae
(Philydor,Xenicopsis,Xenops,etc.) form a transitiongroupleadingup to
the Dendrocolaptinae
and the speciesare schizorhinal
with the exceptionof
Automolus and Anabazenopswhich have the nasal foramen shortened."
Althoughyon Ihering'sdivisionsare not easy to discernit is clear that an
intermediate
conditionof the nasalopenings
existsin membersof the Dendrocolaptidaeand the subfamilyPhilydorinaeof the Furnariidae. An examination of the skinsof theseintermediate
species
of dendrocolaptids
provedeven
moreinteresting,
for in theseformsthe plumagepatternsare in someaspects

alsointermediate.One strikingplumagecharacterthat seemedparticularly
significant
wasa rufouswingstripe(seeFigs.2 and 3) whichoccursin various membersof the Furnariidae,but within the Dendrocolaptidae
is found
only in Glyphorhynchusand Sittasomus. In Dendrocincla anabatina there
is a similarbut more diffusewing stripe. However,Dendrocinclais intermediatein othercharacters.The tail doesnot possess
the striking,stiff,spinelike rectricescharacteristic
of all othermembersof the Dendrocolaptidae
and
is, in fact, morelike the typepossessed
by membersof the Philydorinae.Also
the bill and generalbody shapeof Dendrocinclaappearto be more philydorine-likethan dendrocolaptine.

My ownfield observations,
aswell asthose
of other authors, show Dendrocincla to be intermediatein behavior (see
Feduccia,1970). The speciesof Dendrocincla
hitchup tree trunkslike the
otherwoodhewers,
but alsoforagein a varietyof otherways. Thus,the four
genera, Dendrocincla, Sittasomus,Deconychura, and Glyphorhynchus,although not sharingidentical characters,all possesssome features that are
intermediatebetweenthe Dendrocolaptidaeand Philydorinae.
These"intermediates"
may representsimply"old" formsthat have retained
many primitivecharacters.However, becausethe advanced(derived) character stateswithin the "strong-billed"dendrocolaptidsare indeed those that
are concernedwith tree-trunk foraging, and the "intermediates"(with the
exceptionof Dendrocincla) are virtually identical to the "strong-billed"
woo.dhewers
in their climbingbehavior,the situationis indeed curious. It
would seemreasonableto expectthe evolutiono.f thosecharactersthat increaseefficiencyin climbing and tree-trunk foraging to occur, as has occurred in other unrelatedtree-trunkforaginggroups. One can test whether
or not a given characterstate representsan actual climbing adaptationby
lookingat the samecharacterstatein unrelatedgroupsof birds (see Richardson, 1942).

The possession
by the "intermediates"of charactersintermediatebetween

perchingand scansorialadaptations,plus the possession
of plumageand


1973

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7

,,

Figure 3. The x•ingsof ^!ar,.,arornisrubiginosus(upper left). X{nops mimttns (upper
right). Dendrocittcla attttbtttit•tt(center). Glyphorhynclnt$ .•pirttrtts (1ouer left), and
Sittasomusgriseicapillus (1ox•er right).


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other characterstypical of the ovenbirds,makes the "intermediates"suspect
of being separateevolutionarylines of woodhewerscomingfrom ancestors

that resembledthe present-dayphilydorinefurnariids. Theseformsmay have
reacheddendrocolaptid
gradewith respectto the charactersusedto classify
the family Dendrocolaptidae(= scansorialadaptations), but still possess
many featureswhich reveal a more recentancestryfrom philydorinestock.
In other words, the possibilityof a di- or polyphyleticDendrocolaptidae
cannot be obviated. The alternativeis that the "intermediates"are simply
part of an original mo.nophyletic
radiation of woodhewerswhich have retainedmany "primitive"characters,and are forms occupying"intermediate"
niches.

It wasnot surprising
to find a statement
by von Ihering(1915: 149) that
"... we can presumethat the Dendrocolaptinae
sprangfrom two different
groupsof the Philydorinae." I thereforecontinuedmy investigations
of this
groupin orderto obtainevidenceconcerning
the evolutionarylinesinvolved
in the ovenbird-woodhewer
radiation,while emphasizing
mainly the origin of
the woodhewers.The main focusof this studyhasthereforebeenthe dendrocolaptid-philydorine
boundary,but datafrom the othergroupsof the Furnariidae are used where necessary.I have made the generalassumptionth'at
tree-trunkforagersrepresentthe more derived condition. The assumption
may be logicallyextendedto includea philydorine-likeancestoras a logical
choicefor a pre-dendrocolaptid.This assumptionis not only logical from
anatomicalstudies,but alsofrom zoogeography,
as philydorines

and dendrocolaptidssharea near-commonzoogeographical
range,both reachingtheir
highestdensityin Amazonia.
Anatomicalstudiesoften have failed to solvethis type of problembecause
convergentadaptationsmay mask the actualphylogenies.It seemedto me
that usefulcharactersmightbe found in a comparisonof proteinsof the variousgroups.The useof electrophoretic
patternsof proteinsin systematics
has
beendiscussed
by variousauthorsandwill not be reviewedhere. The reader
is referredto Kitto and Wilson (1966), and Sibley (1970) for examplesof
studiesutilizingelectrophoresis
of proteinsin birds. AlthoughI examined
variousblood, muscle,and eye lens proteins,only with hemoglobins
was I
ableto separatethe two families.
The remainderof this paper is a presentationof variouscharactersof the
ovenbirdsand woodhewersand an evaluationof the positionof the "intermediates"with respectto thesecharacters.After the anatomicalevolutionary
trendsare discussed,
the hemoglobindata are presented,and phylogenetic
considerations are made on the basis of all of the characters.

In the various

sectionsof this paperI have attemptedto answerseveralprimaryquestions.
First, what are the major featuresof the anatomicalevolutionarytrendsin-


1973

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9

volvedin the evolutionof the tree-trunkforaging(derived) woodhewers,and
second,what anatomicaland historicalposition do the "intermediates"occupy?
ACKNOWLEDGMENTS

I am indebted to the following personsand institutionsfor assistance
throughoutthis investigation.The membersof my doctoralcommittee,Robert W. Storer, Claude W. Hibbard, Robert R. Miller, and Harrison B. Tordoff,

providedcriticismandencouragement
duringthe entirestudy. JohnB. Burch
of the MolluskDivisionof The Universityof MichiganMuseumof Zoology
made his laboratoryavailableto me for biochemicalstudies,and Gene K.
Lindsayinstructedme in variouslaboratorytechniques.The Departmentof
Zoologyof The Universityof Michiganand JohnM. Allen providedvarious
piecesof laboratoryequipment.Membersof the Departmentof Biologyof
the Universityof Costa Rica and particularlyDouglassRobinsonprovided
laboratoryspaceand other facilities. CharlesF. Walker of The University
of MichiganMuseumof Zoology,JosephA. Tosi, Jr. of the Tropical Science
Center,and JorgeR. Campabadalof the Organizationfor Tropical Studies

wereof greathelp duringthe CentralAmericanphaseof the study. Maxwell
Cone kindly permittedme to usehis finca for studieswhile I was in Costa
Rica.

Richard L. Zusi of the U.S. National Museum and James H. Hunt of

the LouisianaStateUniversityMuseumof Zoologyprovidedmeasurements
of
certainbones. PeterL. Ames and Mary HeimerdingerClenchprovideduseful
informationabout their doctoraldissertations.Martha B. Lackey skillfully
renderedall of the anatomicalillustrationsexcept Figure 16, and Louis
Martonyitook all of the photographs.Frank B. Gill offeredmany usefulsuggestions
throughout
thisstudy. ArnoldG. KlugeandJohnLundbergoffered
much assistanceand advice with the numerical taxonomy sectionof this
paper. Financialsupportwas providedby a grantfrom the Frank M. Chapman MemorialFund of the AmericanMuseumof Natural History and by a
grant from the National ScienceFoundation,GB-6230, to N. G. Hairston,
The University of Michigan, for researchin Systematicand Evolutionary
Biology.
This paper is a modificationof a doctoral dissertationsubmittedto the
Facultyof The Universityof Michiganin partialfulfillmentof the requirementsfor the Ph.D. degree,1969.
COMPARATIVE

OSTEOLOGY

OF THE

SKULL

Althoughthissectioncoversmostof the skulltypesfoundin the Furnariidae

and Dendrocolaptidae,
it is not intendedas an extensivetreatiseon the skulls
with inclusionof all the minutevariations. Instead,I have attemptedto condensethe variationsinto meaningfulcharacterstatesin eachgroupso as to


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np pmx

A

's

ß
-,?:;:;i';i?i!i!
;!?!;!!!??';'"
....... B

.p
nf

c

\m-p

ib

I cm

bt pr

Figure 4. Dorsal (A), lateral (B), and ventral (C) aspectsof the skull of the woodhewer, Xiphorhynchusguttatus. Abbreviationsare as follows: bt p, basitemporal

plate;bt pr, basipterygoid
process;
e p, ectethmoid
plate;e n, externalnaris;f, frontal;


1973

EVOLUTION

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11

attemptto uncoverthe generalevolutionarytrends,but not all of the intragroupvariation. There is still controversy
concerning
osteological
nomenclature; however,in this paper the terminologyfor skull charactersgenerally
followsthat of Bock( 1963).
ANATOMICAL

MATERIAL

The followingis a list of the skeletalmaterialexaminedduringthe course
of thisstudy: The species
Dendrocincla
fuliginosa,
2 specimens;
D. anabatina,
2; Deconychuralongicauda,2; Sittasomusgriseicapillus,11; Glyphorhynchus
spirurus, 10; Dendrexetastesrufigula, 1; Xiphocolaptespromeropirhynchus,
1; Dendrocolaptescerthia,2; D. picumnus,2; D. platyrostris,3; Xiphorhynchuspicus,3; X. obsoletus,2; X. pardalotus,2; X. guttatus,7; X. flavigaster,
4; X. lachrymosus,1; X. triangularis,7; Lepidocolaptesleucogaster,4; L.
angustirostris,
4; L. affinis, 3; L. albolineatus,3; Campylorhamphus
pusillus,
1; Geositta paytensis, 1; G. cunicularia, 4; Upucerthia dumetaria, 3; U.
validirostris,1; Ochetorhynchusruficaudus,2; O. certhioides,2; Cinclodes
antarcticus,2; C. fuscus,5; C. atacamensis,2; C. taczanowskii,1; Furnarius
rufus, 8; Sylviorthorhynchusdesmursi, 1; `4phrastura spinicauda,4; Phleocryptesmelanops,5; Leptasthenuraandicola, 1; L. aegithaloides,1; L. platensis, 3; Spartanoica maluroides, 4; Schoeniophylax phryganophila, 11; Synailaxis ruficapilla, 1; S. frontalis, 6; S. albescens,4; S. brachyura, 6; S.
gujanensis,2; S. rutilans, 2; Certhiaxis cinnamomea,6; Cranioleucasulphurifera, 2; C. obsoleta,2; C. pyrrhophia,1; C. erythrops,1; `4sthenesdorbignyi,
1; ,4. baeri, 2; ,4. humicola, 1; ,4. modesta,2; ,4. humilis, 1; ,4. hudsoni,2;
Phacellodomus
rufifrons,1; P. striaticollis,8; Coryphistera

alaudina,5; ,4numbius annumbi, 4; Margarornis rubiginosus,4; Premnoplex brunnescens,3;
Pseudocolaptes
lawrencii, 2; Pseudoseisura
lophotes,3; Hyloctistessubulatus,
2; Syndactylarufosuperciliata,16; ,4nabacerthiastriaticollis,3; Philydor lichtensteini,6; P. rufus, 1; ,4utomolusochrolaemus,6; Heliobletuscontaminatus,
1; Thripadectesrufobrunneus,1; Xenopsminutus,3; Pygarrhichasalbogularis,
1; Sclerurusguatemalensis,
1. Alcoholicspecimens
of the followingspecies
were examined: Dendrocinclaanabatina,Deconychuralongicauda,Glyphorhynchusspirurus,Dendrocolaptes
certhia,Xiphorhynchusguttatus,X. lachrymosus,X. triangularis,Lepidocolaptes
souleyetii,Campylorhamphus
pusillus, Synallaxisalbescens,Margarorrdsrubiginosus,Pseudocolaptes
lawrencii,

i p, interpalatine process;i s, interorbital septurn;j b, jugal bar; m f, mandibular foramen (not presentin Xiphorhynchus);m p, mediopalatineprocess;m-p, maxillo-palatine;
m s p, median shelf of the palatine; n, nasal; n f, nasal floor; n-f h, nasal-frontal hinge;
n p pmx, nasal processof the premaxilla; o p q, orbital processof the quadrate; p,
palatine; p p, postorbital process;pt, pterygoid; q, quadrate; t f, temporal fossa; t p,
transpalatine process;v, vomer; z p, zygomatic process.


12

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Hyloctistessubulatus,Automolusochrolaemus
and nestling,Thripadectes
rufobrunneus,and Xenopsminutusand nestling.
WOODHEWER SKULLS

Theskullof Xiphorhynchus
(Fig. 4) is typicalof thewoodhewers
andwill
be usedasthe basisof the description
of the skullsof the group.

Theupperjaw differslittlein basicstructure
fromthatof otherpasserMe
birds,exceptfor theratherlong,slightlydecurved,
heavilyossified
bill. The
bill accounts
for approximately
three-fifths
of the lengthof the entireskull,
butitscharacteristics
aretypically
passerine,
therebeinga long,ovalexternal
naris,andan unossified
nasalsepturn(perforatenaris). The posteriorextent
of thenasalopening
endswellanterior
to thenasal-frontal
hinge;it is therefore holorhinal.The nasal-frontal

hingeis well developedas in mostpas-

serines
as an areaof thinningof the nasalbonesposteriorly;
the sutures
of
the nasalbonesare visible. Thereis a slightdepression
of the frontalbones
at thejunctionof thenasalbones,but theydo not curveanteriorly
overthe
nasals,asin manywoodpeckers.
The actualnasal-frontM
hingeareaappears

verybroadin relationto therestof theskull. Thisis owingnotonlyto the
broadhinge,but alsoto the dorsalarticulations
of the lateralbarsof the
nasalbones,whicharethick andmeetthe frontalbonesat an areaof broad-

ening,andare at approximately
the samelevelas the nasal-frontal
hinge.
The lachrymal
is apparently
absent.The ectethmoid
is a fairlythickbone,
whichis constricted
mesiallyandsendslaterallya bar whichapproaches
the
jugalbar. Thereis a singleforamenwherethe ectethmoid

bonefusesimperceptibly
with the nasalandfrontalbonesandthe orbitalseptumdorsally
andmesially.The orbitalseptumis verywell ossified,
but therearetwomajor

openings
posteriorly,
a fontanelle
postero-dorsally
anda largeforamenfor
thepassage
of theopticnerve.Thereareseveral
smallforamina
for thepassageof othernerves
andvessels.
Theorbitalseptum
endsat theareawhere
theectethmoid
platesmeetmesially,
justbelowthe nasal-frontal
hinge;there
is no extensionof the septuminto the nasalcavity. The postorbitaland
built, but of mediumlength
zygomatic
processes
arepresent;
botharestrongly
ted from each other by the
for passerines.
Thetwoprocesses

arewellsepara
largetemporal
fossa.The remainder
of thebraiit caseis typicallypasserine
withseveral
exceptions.
The supraorbital
areaof 'he frontal bones is extraorlarge, and the two fossae
dinarilybroad,the temporalfossais extremely

ipital region. The quadrate
almostmeeteachotherposteriorlyat the supraoct
is a strong,
well-developed
bone.Therearethreearticularcondyles,but the
lateralcondylemergessmoothly
into the posteriocondyle. There is a large
sesamoid
bonepresentat the posteriorcondylein some specimens.The
quadrate
sends
outa massive
orbitalprocess
thatis expandedat its tip.


1973

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The ventral aspectof the skull is characterizedby being heavily ossified
anteriorlyexceptfor the internasalsepturn,which is essentiallyabsent,and
the floor of the nasal cavity. The maxillo-palatinesare medium-sized,but
the distalendsare not exceptionally
broadened,as in many passetines,
and
only come into slight contactwith the vomer mesially. The palatinesare
situatedfar apart anteriorlyat their fusionwith the premaxillae. The transpalatineprocessis fairly broad at its base,but tapersrapidlymakingan extremelylong, thin structurepointedat its tip. The interpalatineprocessis
present,but short. The mediopalatineplate is constrictedand ends quickly
to give rise to the large mediopalatineprocesses,
which are somewhatfolded
and fuseposteriorlywith the pterygoids.The pterygoidsare heavy and have
prominentdorso-medialprocessesnear the quadratearticulations,which are
the orbital processes
of the pterygoids.The vomeris a short,broad plate of
bonethat is dividedanteriorlyin typicalpasserinc
fashion,but the posterior
diastemacharacteristicof passetinesis obscuredby ossification.The jugal
bars are thin, but strong,and convergeslightlyanteriorlyas they fuse imperceptiblywith the maxillaein a broad area of fusion. The palatineprocess
of the premaxillais not visibleand is probablyfused.Bock (1960: 436)

reportedthe palatineprocessof the premaxillato be presentin all generaof
woodhewers,but the relative degreeof fusion betweenthe processand the
palatinevariesin the differentgenera.He generalized
that the processis only
slightlyfusedin specieswith a long curvedbill, and heavilyfusedin species
havinga short,straighterand heavierbill. In Xiphorhynchus
the processis
slightlyfused. The remainingcharacters
of the baseof the skullappearto be,
in general,typicallypassefine.
Anteriorly,the stronglower jaw is fusedtogetherfor approximatelytwofifths of its entirelength. There are no outstandingfeaturesof the woodhewer
lower jaw exceptfor its sturdystructureand the near absenceof a mandibular
foramen typical of passetines.The foramen is reducedto an almost invisiblevestigeof pinholesize, or is completelyabsent.
The forms that I shall term the "strong-billed"woodhewers,Dendrocolapres, Xiphorhynchus, Xiphocolaptes, Dendrexetastes,Lepidocolaptes,
andCampylorhamphus,
generallyconformin skullcharacters
to the foregoing
description.AlthoughI have not examinedthe skullsof the generaHylexetastes,Nasica,and Drymornis,they appearto be typicalof the groupfrom
externalmorphologyand skull X-rays of study skins. The variation in the
skullsof the "strong-billed"woodhewersinvolvessuch charactersas length
and shapeof the bill, whichvariessomewhatgoingfrom the XiphorhynchusLepidocolaptes
type of moderatelength,somewhatcurvedat the tip, to the
broad-basedtype found in Dendrocolaptes,to the very long, curvedbill of
Campylorhamphus.
However,it is of interestthat the basictype of bill strut-


14

ORNITHOLOGICAL

MONOGRAPHS

NO.

13

ture doesnot seemto alter greatlythe otherskullcharacters.There are minor
differenceswhichwill be treatedin a genericreviewof the groupwhich I am
presentlypreparingbut none that leave any doubt as to a givenbird being
withinthisgroup.
In the wide-billedDendrocolaptes,and in Dendrexetastesand Xiphocolaptes,
the medialpalatineplateis somewhatmoreexpandedthanin Xiphorhynchus.
There is alsootherpalate variationthat seemsto be correlatedwith the type
of bill, but the basic structure is the same. There is some variation in the

amountof ossification
of the nasalregion. This anatomicalseriesbeginswith
less ossifiednasal regions in Lepidocolaptes,Xiphorhynchus,and Dendrocolaptesand proceedsto the greatly increasedossificationin Xiphocolaptes
(with the anterior part of the nasalregion being imperforate) culminatingin
Campylorhamphus
where ossificationhas occurredto the degree that the
nasal openingis a small oval hole. The situation is somewhatdifferent in
Dendrexetastes(one of the very strong-skulleddendrocolaptids)where the
actualnasal openingendsdose to the nasal-frontalhinge, but the skull is
amphirhinal(see Feduccia,1967). It would appear in this case that the
amphirhinalconditionmay be compensation
for the lack of ossificationin the
nasalregion.
OVENBIRD

SKULLS

The descriptionof typical ovenbirdskullsis difficult. While the woodhewersare very uniformwith respectto skull structure,the ovenbirdassemblageshowsgreatdiversity.However,for the purposesof this studyonly two
typesneedbe distinguished,
thosethat are typicallypseudo-schizorhinal,
which
are found in the subfamilies Synallaxinae, Furnariinae, and Sclerurinae
(Pygarrhichasis also pseudo-schizorhinal),and those that tend towards

holorhiny,such as thoseof certain membersof the Philydorinae. Although
onecan otherwisegenerallycharacterizethe varioussubfamiliesof the Furnariidae,they are onlypartiallyseparableby the structureof the skull, sofor this
studyonly the typicalpseudo-schizorhinal
skull and the intermediatephilydorineconditionwill be described.The skullof Asthenes(Fig. 5) is clearly
pseudo-schizorhinal
and formsthe basisfor the description
of that skulltype.
In generalform the skull appearsfragile comparedto the more massive
bonesthat composethe woodhewerskull. The slightlydecurvedbill is small
and thin and constituteslessthan half the lengthof the entire skull. The nasal
septurnis very long and is perforate. There is no ossification
within the sep-

Figure 5. Dorsal (A), lateral (B), and ventral (C) aspectsof the skull of the ovenbird, Asthenes modesta. See Fig. 4 for abbreviations. New terms are: n s, nasal septurn; o p pt, orbital processof pterygoid;and p pm, palatine processof premaxilla.


1973

EVOLUTION

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,np

pmx

A

n-f h

en

p p andz p,fuse

pt

.p
,nf

sp
P
Icm

p pm

c

15


16

ORNITHOLOGICAL

MONOGRAPHS

NO.

13

tum. The longnasalopeningextendsposteriorto the nasal-frontalhinge (inoperativein this case), but is rounded,unlike the "true" schizorhinalconditionof the Charadriiformes,
wherethe nasalopeningendsposteriorlyin a
slit. The nasal-frontalhingeis visibleas an areaof thinningof the nasalbones
posteriorly.The dorsalbar of the uppermandibleis very thin as are the ventral bars. The frontal bonesmeet the nasalssmoothly,there being no anterior curving of the former. The nasal struts, unlike those of the woodhewers,are very thin. The dorsal hingesof the nasal struts are displaced
dorso-caudally,unlike the condition in Xiphorhynchus,where the dorsal
hingesform the lateralareasof the nasal-frontalhinge. Therefore,the actual
area of the nasal-frontalhinge is very constrictedcomparedto that of the
woodhewers.There is very little ossification
of the orbitalseptum,but there
is a small,thin plate of bone anteriorin the septurn,whichmeetsthe mesial
extentof the ectethmoidplates. Unlike the conditionin the woodhewers,a
bony septurnextendsanteriorly just beneath the dorsal bar of the upper
mandible,slightlyanteriorto the nasal-frontalhinge area. No lachrymalis
present,as is alsotrue of the woodhewers,

but the ectethmoidplate is unlike
the woodhewercondition.This broadplatehasvery little mesialconstriction,
and sendsoff a very slightlateral strut that doesnot reach the jugal bar.
The dorsalforamenof the ectethmoid
plateis relativelymuchsmallerthanthat
of the woodhewers,but is single. The lateral bordersof the entire ectethmoid
plate are tilted anteriorly, unlike the woodhewercondition in which the
platesare almostat right anglesto the orbitalseptum.The postorbitaland
zygomatic
processes
arefusedto form a foramenfor thepassage
of the adductor muscle. The temporalfossais small and much more poorly developed
than that of the woodhewers.The supraorbitalarea of the frontal bonesis
constricted,unlike the woodhewer condition and more like the condition

found in most other passerines,
but the remainderof the brain caseshows
no exceptional
features.The quadrateis very weak comparedto that of the
woodhewers.The quadratehasthreearticularprocesses
and, as in the woodhewers,thelateralcondylemergessmoothlywith the posteriorcondyle.However, the lateral condyleconstitutesa broaderarea than in the woodhewers.
A sesamoid,which is retainedin some preparations,is presentat the posterior condyle. The orbitalprocessof the quadrateis thin and the tip is not
expanded.

In ventral view, the skull is generallylessheavilybuilt and showslessossificationthan in Xiphorhynchus.The maxillo-palatinesare very thin, small,

andform a longposteriorly
projectingplateasin mostpasserines,
but fail to
fusewith the vomer. The vomeris a bonyplate,whichlike that of mostpasserines,has a median diastema that extends anterior to the level of the

maxillo-palatines.Anteriorly,the vomer appearsmuch like that of Xipho-


1973

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17

rhynchus,is bifurcat½,but continuesrelativelyfartheranteriorlythan in woodhewcrs. The medianshelf of the palatineis relativelybroaderin Asthenes
than in Xiphorhynchusand other woodhcwcrs.Bock (1960:436-438),
reported on the palatineprocessof the prcmaxillain furnariidsas follows:
"In mostgenera,the processis present,lyingalongthe palatineand not fused
with that bone. In Furnarius. . . the process
lies free in the spacebetween
the palateand the dcntaryprocessof the prcmaxillaand in somewaysresemblesan ossifiedtendon. Rarely is the processfusedor absentas in the
caseof Leptasthenura
or Synallaxis.The lengthof the processvariessomewhatbetweenthe genera."The process
is unfusedin Asthenes.As theycontinue posteriorly,the palatinesdivergelaterallybut do not becomewider
until they mergewith the main bony plate of the palatineposteriorly.The
interpalatineprocessis present,but does not extend far anteriorly. The
mediopalatine

processis small and extendsslightlyposterior.The palatines
are fused to the pterygoidsposteriorly. The pterygoidsshow no special
featuresexceptfor their orbital processes
which are relativelymuch smaller
than in the woodhewers.The jugalsare thin and their anteriorfusionwith
the maxillaeis markedwith a slightchangein anglewith the ventralbar of
the upperjaw. Thereis no contactof the lateralwing of the ectethmoidwith
thejugalbar. The lowerjaw is relativelymuchweakerthanthat of the woodhewersandhasa largemandibular
foramen.
Althoughthere is muchvariationin the skullsof ovenbirds,the basicpattern seemsto remain fairly constantuntil the philydorinesare included(see
next section). The main variation is seenin the amount of ossificationof the
interorbitalsepturn,the positionof the posteriorextent of the nasalopening, and sizeof nasalopening,the shapeof the bill, and the generalstrength
of the entire skull. There is also variation in the postorbitaland zygomatic
processes.In somespeciesthe two processes
are fused,forming a canal for
the passageof the adductormuscle;in other speciesthey are separateand
the temporalfossais larger in thesecases. Also, the ectethmoidplate varies
somewhat,with somespeciesapproachingthe woodhewerconditionof the
character. Aside from these points, there is uniformity in ovenbird skull
anatomy.
PHILYDORINE

SKULLS

The genusAutomoluswill be describedhere as an exampleof the holorhinal ovenbird skull, intermediatein structurebetween the woodhewer and

other pseudo-schizorhinal
ovenbirdskulls. The bill in Automolus(Fig. 6),
like that in mostof the ovenbirds,accountsfor about half the lengthof the
entire skull, but in this genusthe bill is much more heavily built than in

Asthenesand the synallaxines
in general. There is a fairly long, oval-shaped
externalnaris, comparativelyless extensivethan in Asthenes,but more so


18

ORNITHOLOGICAL MONOGRAPHS

NO. 13

n

nppmx

A

is f

•p

,n-f h

,t p
nf

o
mp
J

btp

•

I cm

•

Figure6. Dorsal(A), lateral(B), andventral(C) aspects
of theskullof Automolus

ochrolaemus.SeeFig. 4 for abbreviations.


1973

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than in Xiphorhynchus.The dorsaland ventral bars of the upper mandible
are strongerthan in Asthenesbut weakerthan in Xiphorhynchus.As in other

ovenbirdsthe naris is perforate. The nasal-frontalhinge is visible as an
area of thinningof the nasal bones. The frontal bones meet the nasals
smoothly. The dorsalhingesof the nasal struts are somewhatdisplaced
dorsocaudally,
thoughlessso than in Asthenes,and in generalthey appear
more like thoseof the woodhewers,
wherethey form the lateral bordersof
the nasal-frontalhinge. The skull of Automolusis typicallyholorhinal,and
the externalnaris endsanteriorto the nasal-frontalhinge. The nasal struts
are thicker than thoseof Asthenesbut thinner than thoseof Xiphorhynchus.
The orbitalseptumis like that of Asthenes,therebeinga largepostero-dorsal
fontanelleand an anteriorperforationof the septum,but the bony part of
the septumis of muchstrongermaterialthan that of Asthenes.The anterior
part of the orbital septummeetsthe mesialextent of the ectethmoidplates.
The bony interorbitalseptumextendsonly slightlyanteriorinto the nasal
cavity. The actualectethmoidplatesare more like thoseof the woodhewers;
they are composed
of strongmaterialand are greatlyconstricted
mesially.
They sendout laterallya long thin bar whichmeetsthe jugal bar. The lateral
extensionof the ectethmoidsis tilted slightlyanteriorly,but less so than in
Asthenes;more so than in the woodhewers.There is a singledorsalforamen
asin the otherovenbirdsand in the woodhewers,
but it is relativelylargerthan
in Xiphorhynchus. The postorbital and zygomatic processesare welldeveloped(but lessso than in Xiphorhynchus)and are separated
by a broad
and deeptemporalfossa,similarto that of Xiphorhynchusbut relativelyless
extensive. The supraorbitalarea of the frontal bones is broader than in
Asthenesbut more constrictedthan in Xiphorhynchus. The supraoccipital
regionis somewhatbulgedbut lessso than in Xiphorhynchus.The quadrate

is a strongbonewith three articularcondyles,and like thoseof Asthenesand
Xiphorhynchus,the lateral articular condylesmerge smoothlyinto the posterior condyle,but the jugal articulationis broadenedlaterally,as in Asthenes.
The quadratesendsoff a strongorbital processwith an expandedtip as in
Xiphorhynchus.The vomer of A utomolusis somewhatlike that of Asthenes,
beingbifurcateanteriorlywith a largemediandiastemathat extendsto the
level of the maxillo-palatines
anteriorly. The maxillo-palatines
are thin as in
other ovenbirdsand form a plate that extendsposteriorly,and they almost
meet the anteriorextentof the interpalatineprocesses.The median shelf of
the palatinesis broad as in Asthenesand otherovenbirds.The interpalatine
processes
axe small and extendslightlyforward, and the mediopalatineprocesses
axerelativelylargerthan in Asthenesand are slightlyflaredlaterallyat
their posteriorextent. The palatinesare fusedto the pterygoidsposteriorly.
The pterygoidsare relativelystrongerthan in Asthenesand each sendsoff


20

ORNITHOLOGICAL

MONOGRAPHS

NO.

13

an orbital processof relativelygreatersize. The jugal bars are relatively
thicker than those of Asthenes.

The skull of Automolus,whichis fairly representative
of the philydorine
furnariids,is somewhatintermediatebetweenthat of the majority of the
ovenbirds,
whichhave a weaklybuilt pseudo-schizorhinal
skull, and that of
the woodhewers,
typifiedby the strong,holorhinalskull of Xiphorhynchus.
The upperjaw of Automolusis strongerthan that of the typicalovenbirds,
the externalnarisis of intermediateexpansion,and the nostrilis holorhinal,
but the dorsal articulationsof the nasal strutsare somewhatdorso-caudally
displacedas in the ovenbirds.The ectethmoidplate is more like that of the
woodhewers,but in some respectsis intermediate. The orbital septum is
strongerthan that found in mostovenbirds,but is typicalof the furnariids,
havinglarge fontanelles.The supraorbitalregionis constrictedlike that of
other ovenbirds,but less so than that of the typicallypseudo-schizorhinal
types. The postorbitaland zygomaticprocesses
and the temporalfossaeare
morelike the conditionof Xiphorhynchus
thanthat of Asthenes.Thesecharactersindicatea strongadductormuscle.

In generalthe palateis more like that of most ovenbirds.The vomer is
clearlybifurcatedanteriorly,andthereis a largemediandiastemain thevomer.
The medialpalatineplateis broadlike that of mostovenbirds,and the transpalatineprocesses
are ovenbird-like.The maxillo-palatines
are thin and have
a posteriorlyextendingplate like that of mostovenbirds.The quadratehas
the lateral bulgeof the jugal articulationas in the other ovenbirds,but has a
strongorbital processwith an expandedtip as is typicallyfound in the woodhewers. There is a mandibular foramen in the lower jaw as in the other

ovenbirds.

Most of the philydorinefurnariidsare not quite so intermediatein skull
charactersas is Automolus,and there is a completeanatomicalseriesgoing
from the fragile ovenbirdpseudo-schizorhinal
skull type to the strongholorhinal type found in A utomolus.Most of the philydorinestend to be less
holorhinal than Automolus, with the dorsal articulations of the nasal struts

beingmore dorso-caudallydisplaced.Also, in most speciesthe bill and the
skulls,in general,are of weaker construction.The orbital processof the
quadrateis not expandedat its tip in mostspecies,
and thereis an anatomical
seriesgoingfrom Philydor and Anabacerthiawith no expansionof the tip,
throughHyloctistesand Thripadecteswith slight expansion,to Automolus
whichhasthe tip expandedto the extentfoundin the woodhewers.In mostof
the philydorines
the ectethmoidplate tendsto be morelike that foundin the

Figure 7. Dorsal (A), lateral (B), and ventral (C) aspectsof the skull of Sittasomusgriseicapillus. See Fig. 4 for abbreviations.


1973

EVOLUTION

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n

np pmx

A

is

tn
en

zp

c
msp
mp

bt p
Icm

21